I know there were two revisions:
# Apple part # 661-2302
# Assembly # 820-1094-A
# Apple part # 661-2251
# Assembly # 820-1093-A
But I don't know if rev2 is always ok for dualprocessing
I found also:
"Version 1 and Version 2 logic boards are similar and must be replaced like for like. To differentiate boards, check the EEE code (the last three digits on the serial number bar code). The EEE code is HHQ, HHP, HJZ, HKD, or HL9 for Version 1 logic boards and HQT, J6M, or JVE for Version 2 logic boards."
I know also that I need ASIC revision of the Uni-N greater than 7.